1. Field of the Invention
This invention relates to a method for connecting display panel substrates, and to a device for implementing same.
2. Description of Related Art
A display panel is fabricated by connecting together two substrates. A conventionally used substrate connecting process is now described with reference to FIG. 9. As illustrated in this diagram, a first substrate 110 is held on a first surface table (also known as xe2x80x9cupper surface tablexe2x80x9d) 142 provided with an X-axis driving mechanism 132. Similarly, a second substrate 112 provided with a sealant is held on a second surface table (also known as xe2x80x9clower surface tablexe2x80x9d) 144 provided with a Y axis driving mechanism 134. Whilst observing alignment marks provided on the first substrate 110 and the second substrate 112, the X axis, Y axis are adjusted, along with a xcex8 axis by means of a xcex8 table 162 position beneath the second surface table 144. In other words, the second substrate 112 is aligned in position with the first substrate by rotating it in a horizontal plane by means of a rotating driving mechanism 136. Thereupon, the substrates are pressurized and connected by means of vertical raising and lowering means 138 and a pressure cylinder 160 capable of moving the first surface table 142 or second surface table 144 in the direction of arrow A. Since the gap between the two substrates (hereinafter, called xe2x80x9ccell gapxe2x80x9d) is not uniform, display irregularities occur. Therefore, in order to maintain display quality, it is necessary to maintain an appropriate cell gap. This technology is called xe2x80x9cCell Gap Controlxe2x80x9d. A substrate pressurizing mechanism comprising the aforementioned X axis driving mechanism 132, Y axis driving mechanism 134, rotation driving mechanism 136, vertical raising and lowering means 138, and pressure cylinder 160 is generally known in the prior art, comprising a variety of mechanisms. Therefore, since a mechanism of this kind can be constructed readily by a specialist in this field, detailed description thereof is omitted here.
For example, the connecting process in the fabrication of liquid crystal display elements using glass substrates, or the like, is performed by inserting a spacer made from glass fibre, or the like, together with the sealant, whilst simultaneously scattering a spacer made from resin, silica, or the like, over the entire interior surface of the cell between the substrates. However, this involves a detrimental effect in that the spacers reduce the contrast, and the like. In order to improve display quality, a so-called xe2x80x9cspacerlessxe2x80x9d liquid crystal display is anticipated, wherein precise cell gap control can be achieved without placing spacers inside the cells.
Moreover, in organic EL panels, and the like, which have been the subject of increasing demand in recent years, it is not possible to place spacers on the entire interior surface of the cells, and hence precise cell gap control has not been achieved.
Furthermore, in the case of a liquid crystal display element using glass substrates, or the like, in order to sealing the interior of the cell completely, it is necessary to implement a process for initially placing the sealant, following by a process for sealing the opening section used to introduce the liquid crystal medium by providing sealant on that opening section, and therefore it has not been possible to provide sealant in such a manner that the interior of the cell is sealed completely in a single process. Consequently, the process for sealing the opening section is appended after the introduction of the liquid crystal medium, and therefore it is difficult to guarantee the adhesive strength of the sealed section, thereby giving rise to problems such as leaking of the liquid crystal medium after sealing, or the like.
Furthermore, in the case of an organic EL panel, since it is necessary to expel the air inside the cell when connecting the substrates, in many cases, rather than sealing the panel completely with the sealant, a process is adopted whereby a small gap is left in a portion of the panel and this gap is sealed at the same time that the substrates are pressurized and the cell gap is determined. However, problems frequently occur with respect to the adhesive strength of the sealing of this gap, and as a consequence, the display quality of the panel is degraded, and product lifespan is shortened.
The present invention was devised with the foregoing problems in view, an object thereof being to provide a method for connecting display panel substrates, and a device for implementing said method, whereby, in a substrate connecting process, it is possible to seal the entire circumference of the cell in a single sealing process using a sealant material, in other words, an individual sealing process, whilst simultaneously being able to set the cell gap readily and precisely, to a high degree of accuracy.
In order to achieve the aforementioned object, the method for connecting display panel substrates according to the present invention comprises the steps of:
(1) aligning the positions of and holding a first substrate and a second substrate whereon sealant material is disposed so as to form a waste region in the inner side region of the edges of the first and second substrates;
(2) inserting a spacer in the waste region between the first and second substrates;
(3) setting the cell gap by pressing the first and second substrates;
(4) hardening the sealant material; and
(5) withdrawing the spacer.
In this way, according to the present invention, the sealant material is hardened after the cell gap between the two substrates has been adjusted and determined by the spacer. Therefore, it is possible to readily to set the cell gap correctly to a high degree of accuracy. Consequently, this invention is particularly suitable for use in fabricating organic EL panels, and the like, as well as fabricating liquid crystal panels which employ a so-called pre-connection injection process.
In implementing this invention, if the connection is performed inside an air-tight processing chamber, suitably, a further step of evacuating the processing chamber from normal pressure to vacuum (or vacuum pressure) is included between step (1) and step (2).
In this way, by adopting a composition for causing the substrates to adhere together inside a vacuum processing chamber, in particular, in the manufacturing process for an organic EL panel wherein the material used in manufacture are sensitive to moisture and oxygen, it is possible to eliminate factors which can significantly affect the quality of the panel, whilst being able to control the cell gap accurately by means of a simple process.
A preferred embodiment of the invention includes, between step (2) and step (3), a step of returning the processing chamber in a vacuum state to normal pressure whilst maintaining a pressure difference of substantially zero between the expected cell interior space of the processing chamber and the space outside the expected cell interior space.
By adopting this composition, occurrence of deformation in the substrates is suppressed, and hence the cell gap can be controlled accurately. Therefore, this method is particularly suitable for use in the manufacture process of a display panel using flexible substrates, for example.
Moreover, in a preferred embodiment of the invention, during step (1) to step (4), the first and second substrates are respectively fayed with and held on first and second surface tables, whilst drawing a vacuum between the outer faces of the first and second substrates on the other sides thereof to the mutually opposing inner faces of the substrates, and contact surfaces of the first and second surface tables which respectively confront these outer sides of the substrates.
In this case, in particular, if the connection is performed inside a processing chamber, the air suction power for evacuating the processing chamber as a whole should be less than the air suction power for hermetically sealing the first and second substrates.
By adopting this composition, it is possible to hold the substrates stably without the first or second substrate falling off, and without any divergence in the positions of the substrates with respect to the surface tables, and hence the cell gap can be controlled correctly to a high degree of accuracy.
Moreover, in a preferred embodiment of the invention, if the spacer is constituted by a plurality of three or more spacer elements layered together in a mutually separable fashion, then the cell gap set in step (3) is adjusted by the total thickness of this plurality of spacer elements. Thereupon, after hardening of the sealant material, in step (5), the spacer is removed by, first removing a spacer element located in substantially the middle region whilst leaving the spacer elements contacting and holding the first and second substrates, and then subsequently withdrawing the remaining spacer elements.
By this means, the thickness of a spacer having a connected structure can be adjusted more accurately to match the designed cell gap value. Moreover, if a spacer of this kind is used, then the spacer can be controlled without damaging the surfaces of the substrates, and hence a panel of excellent quality can be achieved.
In a preferred embodiment of the invention, the spacer is constituted by a tapered block-shaped spacer element whose thickness varies at a constant rate, the cell gap set in step (3) being adjusted by withdrawing the spacer from an inserted state.
Moreover, in cases where an additional auxiliary spacer element is appended to the spacer and the total thickness of the spacer and the auxiliary spacer element is set to a greater value than the prescribed cell gap; then in step (2), the spacer with the auxiliary spacer element is inserted in between the first and second substrates; and after step (2) and before step (3), fine adjustment is performed to achieve the prescribed cell gap by withdrawing the auxiliary spacer element.
In this way, fine adjustment of the cell gap can be made by withdrawing the tapered spacer or auxiliary spacer element, and hence more accurate adjustment can be achieved.
In a preferred embodiment of the invention, firstly, an additional auxiliary spacer element is appended to the spacer and the total thickness of the spacer and the auxiliary spacer element is set to a greater value than the prescribed cell gap. Thereupon, the first and second substrates are respectively fayed with and held on first and second surface tables, whilst drawing a vacuum between the outer faces of the first and second substrate on the other sides thereof to the mutually opposing inner faces of the substrates, and contact surfaces of the first and second surface tables which respectively confront these outer sides of the substrates. Next, the processing chamber is evacuated from normal pressure to a vacuum. In this vacuum pressure state, in place of the spacer in step (2), the spacer with the auxiliary spacer element is inserted between the first and second substrates, and the auxiliary spacer element is caused to contact the first substrate.
By this means, since the auxiliary spacer element holds the uppermost positioned substrate in the gravity direction, it aids the holding of the substrate by the surface table, and hence helps to prevent falling of the substrate. In conjunction with this, by creating a vacuum between the substrates and the surface tables, it is possible not only to hold the substrates, but also to suppress deformation of the substrates themselves, and hence more stable cell gap control can be achieved.
Moreover, desirably, in the method for connecting display panel substrates, the hardening of the sealant material is performed by irradiation of ultraviolet light.
Alternatively, the hardening of the sealant material is performed by heating.
Furthermore, in a preferred embodiment, a connecting device for display panel substrates according to the present invention is provided with the following principal components. Namely, this device comprises a first surface table and second surface table for respectively holding a first and second substrate, a spacer, spacer operating means, and sealant hardening means. The spacer has a thickness substantially equal to a prescribed cell gap. The spacer operating means serves to operate the spacer so as to insert the spacer in between the substrates, or withdraw the spacer from same. The sealant hardening means serves to harden the sealant material.
According to this device composition, it is possible to set the cell gap value according to the thickness of the spacer inserted in between the substrates, the set cell gap value being maintained whilst the sealant is hardened, whereupon the spacer can be removed. Therefore, the cell gap can be controlled precisely to a high degree of accuracy, and consequently, a display of high quality can be provided.
A further preferred embodiment of a connecting device according to the present invention further comprises substrate holding means for holding the first and second substrates by respectively sealing them hermetically to the first and second surface tables. This substrate holding means is able to cause the first and second substrates to be respectively fayed with and held on the first and second surface tables, whilst drawing a vacuum between the outer faces of the first and second substrate on the other sides thereof to the mutually opposing inner faces of the substrates, and contact surfaces of the first and second surface tables which respectively confront these outer sides of the substrates.
Moreover, desirably, when implemented, the connecting device according to the present invention comprises: processing chamber defining means for defining a processing chamber for connecting; and pressure adjusting means for changing the pressure of the processing chamber freely from normal pressure to vacuum pressure or from vacuum pressure to normal pressure; the processing chamber defining means being constituted principally by the first and second surface tables.
By adopting this composition, the cell gap can be controlled to a high degree of accuracy, whilst also achieving a compact composition of the device itself.
Moreover, desirably, in the connecting device according to the present invention, the spacer is constituted by a plurality of spacer elements numbering three or more, the respective spacer elements of the spacer being operated and layered in mutually independent fashion, whereby the total thickness of the spacer can be adjusted.
By adopting a spacer having a laminated structure, it is possible readily to make fine adjustment of the cell gap by withdrawing spacer elements, and hence the cell gap can be controlled to an even higher degree of accuracy.
Moreover, in a preferred embodiment of a connecting device according to the present invention, if the spacer is constituted by a single spacer element, then the spacer element should have a shape whereby the cell gap can be altered.
By adopting a spacer composition of this kind, if, for example, the spacer is a wedge-shaped block, in other words, a tapered block, having a thickness which decreases towards the tip thereof at the end which is inserted in between the substrates, then the cell gap can be set according to the thickness of the spacer as determined by the amount (distance or length) by which the spacer element is withdrawn from an initial state of insertion where it has maximum thickness at the outer sides thereof, and hence the cell gap can be finely adjusted to an even higher degree of accuracy.
Alternatively, in the connecting device according to the present invention, desirably, the spacer element comprises a rotating head section composed so as to have a smooth elliptical vertical section; the rotating head section having a shape whereby the cell gap can be controlled by means of the rotating head section contacting the first and second substrates by being rotating within the interval of the waste region.
Moreover, if either one or both of the first surface table and second surface table is a quartz table, then desirably, the hardening means is an ultraviolet light irradiating apparatus. In this case, ultraviolet light can be irradiated directly onto the sealant material from outside the surface table, thereby causing the sealant to harden.
Moreover, desirably, the first surface table and second surface table are heating tables made from metal. In this case, the sealant material can be hardened by heating through heating of the surface tables.